Cells become variable in morphology and function in different regions of the embryo.
The process is

Options

A. differentiation
B. metamorphosis
C. organisation
D. rearrangement

Explanation

**Step-by-Step Solution:**

1. **Understanding the Question**: The question states that cells become variable in morphology and function in different regions of the embryo. We need to identify the process that leads to this variability.

2. **Identifying the Germ Layers**: In embryonic development, the primary germ layers are formed. These are the ectoderm, mesoderm, and endoderm. Each of these layers will give rise to different tissues and organs in the body.

3. **Cell Variability**: Once the primary germ layers are established, the cells within these layers start to change. This change includes variability in their morphology (shape and structure) and function (what they do).

4. **Understanding Differentiation**: The process by which cells become specialized in structure and function is known as differentiation. This means that as cells develop, they take on specific roles that are necessary for the formation of various organs and systems in the embryo.

5. **Conclusion**: Therefore, the process by which cells become variable in morphology and function in different regions of the embryo is termed differentiation.

**Final Answer**: The process is differentiation.

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